## Reversible vs Irreversible formula

kennedyp
Posts: 56
Joined: Tue Nov 13, 2018 12:18 am

### Reversible vs Irreversible formula

What key words should we look for in a word problem that would help us know whether the formula for work should be the reversible or irreversible one?

JasonLiu_2J
Posts: 109
Joined: Sat Aug 24, 2019 12:17 am

### Re: Reversible vs Irreversible formula

If the problem indicates that the system is under a constant pressure, then you would use the w=-P∆V equation to calculate the work done. If the problem instead indicates that the reaction is an isothermic expansion where pressure is not constant, then you would use the equation for a reversible reaction, w=-nRTln(V2/V1).

905373636
Posts: 62
Joined: Thu Aug 01, 2019 12:15 am

### Re: Reversible vs Irreversible formula

JasonLiu_2J wrote:If the problem indicates that the system is under a constant pressure, then you would use the w=-P∆V equation to calculate the work done. If the problem instead indicates that the reaction is an isothermic expansion where pressure is not constant, then you would use the equation for a reversible reaction, w=-nRTln(V2/V1).

Where does the ln(V2/V1) come from?

Daniel Chen 2L
Posts: 101
Joined: Fri Aug 30, 2019 12:15 am

### Re: Reversible vs Irreversible formula

So if the pressure of the system is not constant, then the formula is reversible?

Michael Du 1E
Posts: 117
Joined: Sun Sep 22, 2019 12:16 am

### Re: Reversible vs Irreversible formula

Daniel Chen 2L wrote:So if the pressure of the system is not constant, then the formula is reversible?

correct
while if the pressure of the system is constant, it is irreversible